I've been charging reasonable prices and have made a few sales because of this. It's been, for the most part, an enjoyable experience.

A couple of weeks ago, I sold an early Punisher appearance. The issue was in very good condition and I included lots of photos in my listing to indicate this. My price was pretty reasonable (under what other similar issues had sold for). 

I was contacted by a potential buyer and offered a price below my advertised price. I responded with a counter-offer which the buyer accepted and paid. Out of interest, I checked out the buyers feedback. Their transaction level was fairly low (around 70) but they showed a feedback score of 100%.

I don't know why (maybe some wording in their message) made me a little suspicious. I double checked every inch of the comic and took photos before packing and shipping it as securely as possible with recorded delivery. 

The delivery was accepted successfully two days later and all seemed well (especially as the buyer then gave me positive feedback and praised me on the speed and packaging).

Flash forward to a week later. Still being polite, the buyer messaged me with a comment along the lines of "Just had a closer look at the issue and have noticed a crease near the bottom of the cover. I still want this issue but this is obviously not as good a condition as was advertised so I'm not sure what to do."

From this, I assumed that the buyer was looking for a partial refund. Instead, I offered to take the issue back for a full refund and cover the cost of postage. The buyer went quiet for a couple of days and then messaged me once more, saying that he'd noticed another flaw. Again, I offered to take the issue back and did not receive a reply.

On a whim, I decided to investigate this guy a bit more, and this is where things came to light. Some of the positive feedback that he had received was along the lines of 'difficult customer who made false claims about condition.' (yep - I discovered that a seller cannot leave negative feedback for a buyer!).

So, here's what I did. 

I looked at this guy's feedback left for sellers (there were lots of negative ratings about quality) and also looked at his transactions over the last few months. Then I copy/pasted what had happened to me and sent it to lots of those sellers, receiving dozens of responses which echoed my own experience. Many of these honest sellers just gave full or partial refunds without question.

So basically, the guy's scam is this:

1) Receive the item and get positive feedback. 

2) Contact the seller with a false claim.

3) Hope to get a full or partial refund with every transaction (and because the messages between buyer and seller are private, none of this is broadcasted. Loophole!).

Bottom line is that I've blocked this guy and reported him to eBay and half a dozen of his victims have done the same. Waiting on what happens now (eBay have already told me that they treat claims seriously but will not inform me of the outcome, so I'll just have to see if he's still active in a few weeks).

Sorry this is such a saga - but I just wanted to highlight one of the pitfalls of eBay (of which, I'm sure, there are a few).

If I buy original art on eBay now it's from the artist only.

Not being able to give negative feedback to buyers is the main reason I'd never sell on there myself.

 In truth,  originally,  the sellers typically left feedback first,  after payment. So,  it was mostly the buyers who retaliated with negative feedback.  In these instances, it was a form of extortion.  Ebay's policies more often than not facilitate scamming by the buyer.

My advice: Fight any unfair claims such a scammer might open against you. Keep all correspondence regulated to eBay's own message system.  It will protect you, as the company can access those messages and see if the buyer is trying to extort you, through threat of opening a case or negative feedback.  Be professional! Do not let a scammer, or even a legitimate,  but upset buyer drag you into a flame war. 

I have won on appeal against such scammers, so it can happen that a seller can succeed against such scamming. In fact,  I helped instruct a friend the past week who faced a situation much like your own,  Craig. He won the case, I am happy to report. 

Sounds like you also have done the right thing in reporting the scammer, warning other sellers, and blocking that buyer. But do NOT leave "positive" feedback that is actually a negative response. I realize sellers frustrated with not being able to leave actual negative feedback want to vent or warn others through the positive feedback,  but in the end you are simply adding another positive number to the scammers total. As you saw with your own case, Craig,  it misleads you when you don't actually read the text into believing the positive comments are legitimate. 

Ebay has finally tried to even things a tad more in the past couple of years,  but overall it's still tilted more in the buyer's favor. Ideally,  BOTH sellers and buyers should be protected. The scams come both ways. Both parties should feel safe when participating and making transactions on the site.

I've been selling on eBay for 25 years (Gah!!!), so I know full well its problems and pitfalls. Over on the CGC* message boards, sellers have a continuously updated list of scammers and bad buyers posted so the names can be added to sellers' blocked bidders list:

Blocked User List 

It's definitely helpful in avoiding the rotten scammers.

*I should note, I'm not a fan of slabbing comics, but I do use the CGC site for information and such in my capacity as a comic book reseller. 

The thing is, to avoid buyers feeling short-changed, I tend to undergrade the comics I'm selling. I don't see the point in selling something which is likely to cause disagreement. I also tend to give positive feedback as soon as someone has paid - after all - that's their part of the deal, right?

I would never give 'false positive' reviews for the reason mentioned (it skews the seller's profile into a more positive one).

I've been selling on eBay for decades, but recently for the first time got a similar message back from a buyer: grateful for the comic, but it's not in the condition listed, and etc.

However, he said it must have been damaged in transit, and would have been better if I had bagged/boarded it (I had); and also that because I had packaged it so securely that *maybe he had damaged it in unwrapping it.

I chose to ignore it, because he had as much as admitted that it was possible that he had damaged it, and also that it was securely packaged; nothing could be gained in engaging with him.

I just checked his rating, and there isn't a pattern of this, so I'll assume he wasn't purposely trying to scam me.

But that would only come to light if he wasn't using the delaying scam that my guy did, and only be obvious if the sellers gave 'false positive' reviews which you could see.

If he's a regular comic buyer, you could message his recent sellers with a low-intensity message just to see if they've experienced anything similar.

I only suggest this because if you blank him and he feels aggrieved (or is trying to con you), he may decided to open a dispute against you.